Useful next calculations
Rates and sources
UK energy unit rates vary by region and supplier. Ofgem publishes a price cap refreshed each quarter.
Source: Ofgem — Energy price cap. Check the linked guidance and any live quote before acting.
When to use this calculator
- Before switching supplier, upgrading equipment or comparing energy-saving changes.
- When you want to test different usage or price scenarios quickly.
- When you need a simple estimate before requesting installer or supplier quotes.
- When a tariff is about to change and you want to model the bill impact.
A worked example
These are the example figures the calculator opens with.
| Input | Value |
|---|---|
| Electricity Per Year (kWh) | 2,900 |
| Electricity Rate (p/kWh) | 24 |
| Gas Per Year (kWh) | 11,500 |
| Gas Rate (p/kWh) | 5.5 |
For those figures the calculator returns:
- Electricity: £696.00/yr
- Gas: £632.50/yr
- Total: £1,547.50/yr
- Monthly: £128.96
Method & assumptions
This combined energy bill calculator brings together your gas and electricity costs into a single annual and monthly estimate, reflecting the way most households receive and think about their energy expenditure. It applies the unit rates and standing charges you enter for each fuel separately, so it is important to enter figures from your actual tariff rather than national averages, as rates differ between suppliers, regions, and tariff types. The calculation assumes consistent monthly usage, whereas in practice gas costs are heavily front-loaded into winter months. The tool is most useful for budgeting and for comparing the impact of switching tariffs or reducing consumption. It does not model direct debit smoothing, which many suppliers use to spread costs evenly across the year regardless of seasonal variation.
Common mistakes
- Using the current tariff without testing a higher unit rate.
- Forgetting the standing charge when comparing annual bills.
- Treating the result as a supplier quote.
- Using optimistic savings figures for an upgrade without a written estimate.
What to do next
- Run the same scenario with a 10% higher unit rate.
- Compare this result with a related energy calculator before requesting installer quotes.
- If you are evaluating an upgrade, rerun with actual quote figures.
- Set a reminder to rerun the calculation when your tariff renews.